Arc indicator system for projection lamps



July 26, 1938. N. BRENKERT ARC INDICATOR SYSTEM FOR PROJECTION LAMPS 2 Sheets-Sheet 1 INVENTOR. Re r f M ATTORNEY.

B 916M Bren l/M July 26, 1938. Y N. BRENKERT ARC INDICATOR SYSTEM FOR PROJECTION LAMPS Filed Jan. 29, 1937 2 Sheets-Sheet 2 INVENTOR.

BY v/ Neal Drenkerf ATTORNEY.

Patented July 26, 1938 I UNITED STATES PATENT OFFICE ARC INDICATOR SYSTEM FOR PROJECTION LAMPS 2 Claims.

The present invention pertains to a novel are indicator system for projection lamps, particularly of the type employing carbon electrodes.

Lamps of earlier construction are equipped with an arc indicator screen mounted on the top of the lamp, and in the transverse verticalplane of the arc to maintain the image upright. While the arc may be satisfactorily projected on the screen, the position of the screen is such that it frequently cannot be seen conveniently by the operator. In order to see the image ofthe are on the screen, he is obliged to move his body considerably to one side or the other of the axis of the machine, thereby taking his attention from other operations that must be simultaneously performed at the rear end of the machine. This is particularly annoying to operators of .short stature, and as a result, the operator often fits-anelevated bracket upon the lamp housing to hold the screen, or causes the arc image to be projected on the ceiling of the projection room.

Either of these expedients is obviously awkward.

and unsatisfactory, as will be recognized by those skilled in the art.

One of the objects of the present invention is to mount the screen in a more convenient position, offset from the transverse vertical plane of the arc, and at the same time project an upright image on the screen. The screen is so positioned that the image may conveniently be seen by the operator while he is adjusting the controls at the rear end of the machine, without introducing any awkwardness in the mounting of the screen or its supporting parts. Such offset position of the screen, which may be either forward or rearward, avoids interference with the chimney that stands directly over the arc. i

Another object of this invention consists in providing a novel and unique mirror arrangement for imaging the arc in the desired-upright position, as will appear more fully hereinafter.

The invention is fully disclosed by way of example by the following description and the accompanying drawings, in which Figure l is a side elevation of a lamp housing equipped according to the invention; Figure 2 is a rear end view thereof;

Figure 3 is a section on the line 3-3 of Figure 1;

Figure 4 is a section on the line 4-! of Figure 2; I

Figure 5 is a section on the line 5-5 of Figure 4, and V Figure 6 is a section on the line 6-6 of Figure 4.

Reference to these views will now be made by use of like characters that are employed to designate corresponding parts throughout.

In Figures 1 and 2 is shown a lamp housing I of known design except for the particulars speci- 5 flcally described herein. From the rear wall of the housing extends a protuberance 2 for containing certain parts of the feeding mechanism which may be adjusted by hand at the knobs 3.

The housing contains a pair of electrodes 4 and 10 5 that form an arc 6. To a side wall of the housing, at some distance above the arc and above the door I, is secured a bracket 8 (Figure 3) formed with a mirror frame 9. In the frame is mounted a mirror it) held in position by a split 1 ring ll.

From the bracket 9 a lens tube i2 extends through a hole I3 formed in the housing ,I. This tube is positioned so that its axis intersects the arc 6 as may be seen more clearly in Figures 1 20 and 2. The tube l2 contains a spacer tube l4. At the ends are plane-convex lenses I5 facing one another- The upper lens l5 bears against a coil spring 16 mounted in the upper end of the tube 12. A screw tube I1 is threaded in the lower end 5 of the tube l2 and bears against the lower lens l5, whereby both lenses and the spacer tube H may be adjusted as a unit in the tube I2.- The adjustment is secured by means of a lock nut I8 threaded on the screw tube l1 and bearing against 30 the lower end of tube l2.

-At a higher point on the lamp housing, and on the same sidejis mounted another mirror by the means now to be described. At this point is formed an ear IS on the housing near the end 35 wall thereof.- Through the ear is passed a headless .bolt 20 having an acorn nut 2i screwed on its outer end and bearing against the ear l9.

-On the other end of the bolt'is loosely mounted a collar 22. Through the collar and the bolt is 40 passed a right-angled pin 23 for carrying the remaining mirror frame as will presently be described. It may be seen, however, that tightening of the nut 2| tends to draw the bolt through the collar 22, thereby binding the pin 23 by a shearing'action between the bolt and the collar.

As already indicated, the pin 23 serves to support another mirror frame 24, passing through a lug 25 thereon. A mirror 2'6 is mounted in the frame 24 and held by a spring ring 21 as shown in Figure 4. The mirror 26 is positioned to receive light from the mirror l0 and project it upon an indicator screen as will now be described.

For supporting this screen, a frame 28 is secured to the rear wall of the lamp housing and the mirror frame 24.

at an elevation preferably slightly higher than The rear end of the chim4 ney 29 has been found to be a suitable place for mounting the frame 28.

The screen. mounted in the frame 28 is of suitable material, such as frosted glass, so that the image projected thereon from mirror 26 may be seen from either side. The screen has gaugev image more distinct and readily visible.

With the screen in the position described,-the image may be seen by the operator without taking his attention from the controls 3. Only a slight movement of the head is necessary, whereas a screen mounted upon the chimney as formerly requires the operator to stoop forward and swing his body sidewise. These movements are so awkward that the operator frequently prefers to discard the screen so mounted and provide some other means, usually improvised, for showing the image.

The screen mounted in the position herein described, although projecting from the housing, is disposed in the angle between the rear wall of the housing and the top of the protuberance 3 and is shielded within this angle so that it does not impede the movements of the operator about the machine.

In order that the are 6 be projected rearwardly to the screen, both mirrors i0 and 26 are tilted somewhat rearwardly as illustrated. The mirror ill nearer to the arc requires no adjustment after assembly and its frame 9 is held .in a fixed position with the bracket 8. The image of the arc 6 is projected by mirrors to the screen 30 along the arrows shown in Figures 1 and 2.

Slight but accurate adjustments of the upper mirror 28 may be necessary. The mounting described permits adjustment in three directions. The assembly is rotatable towards and away from the lamp housing by turning the bolt on its axis before tightening the nut 2!. Another adjustment, lengthwise of the housing, is made by turning the pin 23 in the collar 22 and bolt 20 before tightening the nut 2!. The thirdadjustment, perpendicular to the bolt 20, is made by shifting the pin 23 in the bolt 20 and collar 22 before tightening the nut 2!.

The mirror frame 24 is fixed to the pin 23 by any suitable means such as a pin 33 driven through the pin 23 .and lug 25 of the frame.

It is important that the image be shown upright on the screen. Heretofore there has been no difllculty in this connection, as the screen was positioned in the transverse vertical plane of the arc, and it was only necessary to mount the mirrors perpendicular to said plane with their centers in said plane. In the present construction, a more particular arrangement of the mirrors is necessary to project the arc rearward to the screen and yet maintain the image in an approximately in the transverse vertical plane of theme, and the upper mirror 25 is offset from this plane in the direction towards the screen 30, or along the longitudinal axis of the housing. It has previously been customary in the art, where two mirrors were used, to mount the upper mirror directly over the lower mirror, but in the oflset position of the' screen relative to the transverse vertical plane of the arc. it was found that such an arrangement of mirrors caused the image of the arc to be other than upright on the screen. The offset position of the upper mirror 26 and the angular adjustments of both mirrors, presently to be described, resultsin an upright image on the screen and are therefore important in this invention.

The lower mirror it is tilted away from the vertical axial plane of the housing to reflect upwardly and is also turned on a vertical axis towards the upper mirror 26 to reflect into the same. Similarly, the upper mirror 26 is positioned at the proper angle to the transverse vertical plane of the arc to reflect to the level of the screen 86 and is further turned on avertical axis to throw a beam of light laterallyupon the screen at.

In the scale of dimensions illustrated in the drawings, the following angular adjustments of the mirrors result in an uprightimage on the screen 3c: the lower mirror it is tilted 22 away from the vertical axial plane of the housing and is turned on a vertical axis to an angle of 17 towards the upper mirror 26. The adjustment of the upper mirror 26 thenfollows as a matter of course, as it is only necessary that this mirror be focused upon the screen 88. Thereupon, an

upright image of the arc is produced as a consequence .of the mounting of the mirror ill previously described. Precise adjustment of the mirror 26 is obtained by turning the bolt 2% and sliding and turning the pin 23 in the manner already set forth.

Although a specific embodiment of the invention has been illustrated and described, it will be understood that various alterations in the details of construction may be made without departing from the scope of the invention, as indicated by the appended claims.

What I claim is:

1. In combinationwith a projection lamp housing, animage indicator screen mounted on the rear wall thereof, a mirror mounted on said housing and positioned to receive light from the interior of said housing, an ear formed on said housing between said mirror and screen, a bolt in said ear, and another mirror supported by said bolt and positioned to reflect light from the first mirror to said screen, a collar loose on said bolt, a pin passed through said collar and bolt, and means for tightening said bolt in said ear, and another mirror supported by said pin and positioned to reflect light from the first mirror to said screen.

a 2. In combination with a projection lamp housing, an image indicator screen mounted on the rear wall thereof, a mirror mounted on said housing and positioned to receive light from the interior of said housing, an ear formed on said housing between said mirror and screen, a bolt in said ear, a pin lengthwise rotatably adjustable in said bolt, and another mirror carried by said pin and positioned to reflect light from the first mirror to said screen.

NEAL BRENKERT. 

